Checking the starter

Since an internal combustion engine cannot start by itself, a functioning starter is essential for a roadworthy vehicle. Malfunctions can be caused, for example, by incorrect connections, faulty solenoid switches or a damaged single-pinion gear. Learn everything about possible problems and how you can remedy the individual cases here.

The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for suitably qualified personnel only.

Design and function of the starter

A starter motor is usually composed of the following assemblies:

Electric starter motor
Engaging relay (solenoid switch)
Drive-end bearing with single-pinion gear

The electric starter motor consists in principle of a tubular pole housing in which the pole shoes, excitation windings and permanent magnets are housed. The electrical armature with armature winding is situated in this pole housing. The engaging relay, also known as a solenoid switch, is a combination of a relay and solenoid magnet, and is mounted at the top in the drive-end bearing. The single-pinion gear with pinion, free-running roller, engaging lever, carrier and in-line spring is situated in the drive-end bearing.

Function

The engaging relay is actuated when the motor is started via the ignition lock. The flow of current in the pull-in and hold-in winding attracts the relay armature. This actuates the engaging lever and pushes the carrier unit with pinion and freewheel against the ring gear of the engine flywheel. Once the pinion is fully engaged, the contact bridge in the engaging relay completes the main circuit to the starter motor. The starter is switched on and turns.

Testing the starter

Electrical faults in the starter are mainly caused by overloads. This can manifest itself in ground and winding short circuits in the field and armature winding, but sometimes also in the coils of the control elements (solenoid switch). Carbon brushes and collectors are subjected to high loads and are more susceptible to faults than the alternator. While, for example, clamping carbon brushes in the alternator do not cause voltage to arise and thus relieve the alternator, clamping carbon brushes in the starter leads to the formation of significant arcs due to the high currents. These arcs often destroy the collector. A multimeter and a clip-on ammeter are required for troubleshooting. Fault sources (such as the pinion) can, however, also be located through acoustic perception. Please also refer to the technical info: " Ground (31) ".

The starter does not turn when the ignition switch is actuated.

Cause:	Remedy:
Switch on lighting (low beam).
Lighting weak or not working = Break in the cable or ground connection Insufficient current flow due to loose or oxidized connections Battery discharged Alternator faulty	Check battery cables and connections Clean battery poles and terminals Electrically secure connection between starters Connect battery and ground Measure battery voltage Check battery, if necessary charge or replace Check alternator
Solenoid switch does not energize: Bridge terminals 30 and 50 on the starter, Starter runs / engages = Ignition switch faulty or Break in the cable	Replace ignition switch Repair break
Solenoid switch energizes: Remove battery cable from terminal 30 on the starter and connect directly to the contact screw below connection terminal 30. Starter starts up = Solenoid switch contacts contaminated or worn	Clean/replace solenoid switch and contacts

Starter does not turn when the battery cable is connected directly to the contact screw below connection terminal 30, or the starter turns too slowly, or does not crank the engine.

Cause:	Remedy:
Carbon brushes worn	Replace carbon brushes
Carbon brushes clamping	Clean carbon brushes and guides of the brush brackets
Springs not supplied with sufficient voltage. Carbon brushes not contacting	Replace springs
Collector contaminated	Clean collector
Collector grooved or burned	Refurbish or replace starter
Armature or field winding faulty	Refurbish or replace starter

Starter engages and energizes. The motor only turns jerkily or not at all.

Cause:	Remedy:
Battery discharged	Charge battery, check
Poor conductance of electricity due to loose or oxidized connections	Clean battery poles and connections and tighten
Carbon brushes clamping	Clean carbon brushes and guides of the brush brackets
Carbon brushes worn	Replace carbon brushes
Collector contaminated	Clean collector
Collector grooved or burned	Refurbish or replace starter
Armature or field winding faulty	Refurbish or replace starter

Drive pinion does not disengage. Starter engages and energizes. The motor only turns jerkily or not at all.

Cause:	Remedy:
Drive pinion faulty	Replace drive pinion
Ring gear on the flywheel faulty	Rework ring gear, replace if necessary

Drive pinion does not disengage.

Cause:	Remedy:
Pinion or steep thread contaminated or damaged	Refurbish or replace starter
Solenoid switch faulty	Replace solenoid switch
Return spring worn or broken	Replace return spring